RESUMEN
Motivated by recent experiments on the rod-like virus bacteriophage fd, confined to circular and annular domains, we present a theoretical study of structural transitions in these geometries. Using the continuum theory of nematic liquid crystals, we examine the competition between bulk elasticity and surface anchoring, mediated by the formation of topological defects. We show analytically that bulk defects are unstable with respect to defects sitting at the boundary. In the case of an annulus, whose topology does not require the presence of topological defects, we find that nematic textures with boundary defects are stable compared to defect-free configurations when the anchoring is weak. Our simple approach, with no fitting parameters, suggests a possible symmetry breaking mechanism responsible for the formation of one-, two- and three-fold textures under annular confinement.
Asunto(s)
Bacteriófago M13/química , Cristales Líquidos/química , Modelos Teóricos , Simulación por Computador , Modelos QuímicosAsunto(s)
Erupciones por Medicamentos/etiología , Interleucina-3/efectos adversos , Urticaria/etiología , Diafragma , Eritema/etiología , Femenino , Humanos , Inyecciones Subcutáneas , Interleucina-3/administración & dosificación , Mesotelioma/terapia , Persona de Mediana Edad , Neoplasias de los Músculos/terapia , Neoplasias Torácicas/terapiaRESUMEN
A middle-aged woman with common variable immunodeficiency noted a papular skin eruption that simulated Gottron's sign of dermatomyositis on the dorsal hands. Examination of a skin biopsy specimen demonstrated noninfectious granulomatous inflammation. The patient was subsequently found to have visceral granulomas when examined using laparotomy. Noninfectious granulomas of the viscera and integument have been previously reported in patients with several immunodeficiency syndromes, including common variable immunodeficiency.
Asunto(s)
Inmunodeficiencia Variable Común/complicaciones , Granuloma/etiología , Enfermedades de la Piel/etiología , Adulto , Femenino , Granuloma/tratamiento farmacológico , Humanos , Prednisolona/administración & dosificación , Piel/patología , Enfermedades de la Piel/tratamiento farmacológicoRESUMEN
BACKGROUND AND OBJECTIVE: We identified several patients with a histologic diagnosis of pretibial myxedema in whom thyroid disease was not found. The purpose of this study was to investigate if histologic characteristics can distinguish between pretibial mucinosis secondary to Graves' disease and that unassociated with thyroid disease. METHODS: Biopsy specimens interpreted as compatible with pretibial myxedema were reviewed; these included 12 cases of pretibial mucinosis with documented Graves' disease, and six cases of pretibial mucinosis without evidence of Graves' disease. Ten specimens interpreted as compatible with stasis dermatitis were also evaluated for histologic characteristics, including the possible presence of mucin. RESULTS: Features that distinguish between pretibial mucinosis associated with Graves' disease and pretibial mucinosis without Graves' disease included preservation of a zone of normal-appearing collagen in the superficial papillary dermis (12/12 with Graves' disease, 0/6 without), mucin deposition in the reticular dermis (12/12 with Graves' disease, 0/6 without), lack of mucin deposition in the superficial papillary dermis (11/12 with Graves' disease, 1/6 without), angioplasia (2/12 with Graves' disease, 6/6 without), and the presence of hemosiderin (2/12 with Graves' disease, 6/6 without). Mucin deposition in the papillary dermis was found in six of 10 specimens interpreted as stasis dermatitis. CONCLUSIONS: There are patients with pretibial mucinosis in whom there is no thyroid disease. Specimens from patients without Graves' disease have features of stasis dermatitis in addition to mucinosis. We conclude that pretibial mucinosis may result from stasis or Graves' disease and that histologic differences allow for accurate differentiation.
Asunto(s)
Enfermedad de Graves/complicaciones , Dermatosis de la Pierna/patología , Mixedema/patología , Diagnóstico Diferencial , Enfermedad de Graves/patología , Humanos , Dermatosis de la Pierna/etiología , Mucinas/análisis , Mixedema/etiologíaRESUMEN
Peculiar fingernail hemorrhages appeared in a febrile, comatose patient several weeks after she was admitted to the hospital. Bedside questioning of the nursing staff uncovered a frequently used neurologic examination maneuver as the cause. We suggest the term "pen push purpura" to describe this phenomenon. The clinical significance and various causes of nail bed hemorrhages are reviewed.